The long term objective of the applicant is to develop effective therapeutic interventions for the treatment of acute high-permeability lung edema. This condition afflicts over 150,000 U. S. citizens/yr. Rational therapy will be based on a detailed understanding of the mechanisms by which the lung parenchyma is injured. Substantial evidence supports the hypothesis that oxidants generated by cells either native to or sequestered within the lung may contribute to this injury. This application focuses on the mechanisms whereby oxidants H202 and 0 from chemical-generating systems or oxidants generated by stimulated leukocytes) injure human microvascular endothelial cells, cells of the isolated perfused rabbit lung, and cells of the intact rabbit lung subjected to oxidant injury. The proposal is a direct extension of observations made in a cultured cell line; there, oxidant injury results in DNA single strand breaks, activation of polyADPribose polymerase, consumption of cellular NAD, and arrest of glycolysis and high-energy phosphate formation. This application hypothesizes that that same mechanism is responsible for oxidant injury of lung cells, and proposes to test that hypothesis in cultured lung cells and isolated and in vivo lungs. Following attack by the different oxidants, direct measurements of DNA strand breaks, polyADPribose polymerase activation, NAD depletion, glycolysis, and ATP will be made. Interventions with inhibitors of polyADPribose polymerase will be made to test the hypothesis that cell death or lung injury is dependent upon activation of this enzyme. Comparison of the sensitivity of different lung cell types to this mechanism of injury will be made in parallel with measurements of the intrinsic cell antioxidants (catalase, SOD, glutathione).